In dialog systems, a single user input may refer to more than one domain and user dialog act (aka intent) for each of these domains. A Natural Language Understanding System (NLU) typically is used for a small number of domains (e.g. 1, 2, . . . ). When more domains are to be supported, the scaling of an NLU system can be challenging. For example, adding a new domain to an existing language understanding system adds additional new models. Each new language added to the NLU system also adds additional models.